Method and apparatus for drying the adhesive on closing flaps of flat-bags and envelopes and the like



Dec. 27, 1966 R. WINKLER ETAL METHOD AND APPARATUS FOR DRYING THEADHESIVE ON CLOSING FLAPS OF FLAT-BAGS AND ENVELOPES AND THE LIKE 2Sheets-Sheet 1 Filed Aug. 4, 1964 L o R r o o o L O EL Q 0k. w -hUIQ d 5.l. D Q 6 t ill. 7, QQQ w A c 2 w s h V H W m w DIMEPE 2 R. WINKLER ETALMETHOD AND APPARATUS FOR DRYING THE ADHESIVE ON CLOSING FLAPS 0FFLAT-BAGS AND ENVELOPES AND THE LIKE Filed Aug. 4, 1964 Dec. 2 7, 1966United States Patent Ofiice 3,293,765 Patented Dec. 27, 1966 3,293,765METHOD AND APPARATUS FOR DRYING THE ADHESIVE ON CLOSING FLAPS FFLAT=BAGS AND ENVELOPES AND THE LIKE Richard Winkler,Burgermeister-Winkl Strasse, Rengsdorf uber Neuwied am Rhein, Germany,and Kurt Diinnebier, Am Birkenhang, Glatlbach, Germany Filed Aug. 4,1964, Ser. No. 387,415 Claims priority, application Germany, Aug. 17,1963, W 35,112 14 Claims. (Cl. 341) The drying of the adhesive on paperor the like sheet material, particularly on the closing flaps offlat-bags, envelopes or the like (hereinafter termed only flat-bags)hitherto required a comparatively long time and long drying paths and soprevented a rise in the output of the machines for producing these fiatbags. In addition, the expenditure of energy for the heating of the airdisplaced by blowers and generally used for the drying, is substantiallytwice as high as the energy needed for the drive of the machine, becauseof the inevitable heat losses.

Attempts have already been made to dry the adhesive on the closing flapwith infrared rays in a shorter time and over shorter paths. This wasalso successful up to a certain extent. The intensity of the drying is,however, limited by the blistering of the solvent in the adhesive withexcessive heating and by the curling up of the paper during the dryingof the strips of adhesive applied only at the margin. Admittedly thepower re quirements for infrared drying are only about equal to thedriving power for the machine. But infrared drying in the production offiat-bags involves a great risk of fire because, in the event of asudden stopping of the machine as a result of disturbances which cannever be completely avoided, the paper under the infrared radiators,which continue to glow for a long time, catches fire or at least becomescharred. It is true that the infrared radiators may be automaticallyswung out on stopping the machine, but this means a further complicationof the installation.

The object of the invention is to overcome the said disadvantages and toincrease the drying capacity of the machines with a simultaneousreduction in the power consumption for drying. This object of theinvention is achieved by drying the adhesive, which may be of anysuitable type and is hereinafter called gum, applied to the closingflaps, by means of the heat generated in this adhesive itself in ahigh-frequency electric field. The energy losses in high-frequencydrying are at a minimum in comparison with the above-mentioned types ofdrying so that, with the same conditions otherwise in an envelopemachine for drying the closing-lap gum, there is a ratio of about 12 kw.for the drying with a hot-air blast, -6 kw. for drying with infraredradiators 22.5 kw. for high-frequency drying.

In practice, the high-frequency drying is carried out in such a mannerthat the freshly gummed closing flaps of the fiat bags travel under orover two or more rodshaped electrodes at the conveying speeds existingin the machine. Between the electrodes there is generated an electricfield of high frequency which becomes concentrated in the moist layer ofadhesive which is a good conductor, and to some extent also in the moistpaper, and heats and dries both from the inside. The path of travel ofthe parts to be dried is substantially parallel with the longitudinaldirection of the electrodes.

According to another embodiment, the freshly gummed closing flaps to bedried are conveyed through the interior of a slotted waveguide, in thelongitudinal direction of this waveguide in which there is ahigh-frequency electric field which extends perpendicularly to thesurface of the paper. In this case the effect is the same as in thefirst case.

Flat bags conveyed individually through the machine are preferably heldflat at the closing flaps to be dried, on a conveyor belt of a materialwhich does not convert the high-frequency electrical energy into heat initself, for example Teflon, i.e. a fluorocarbon resin of the characterhereinafter more fully described. If the machine stops, there is nodanger of the paper burning even if the highfrequency installation isswitched on.

Preferably mounted to one side of a fiat-bag carrier is a high-frequencygenerator, the output terminals of which carry, on holders, rodelectrodes which are substantially parallel to the direction of travelof the carrier and which produce between the and substantially parallelto the surface of the paper, a high-frequency electric field. If thegumming of the closing flaps of the flat bags is relatively wide, therod electrodes, which are parallel with one another and spaced at anappropriate distance in relation to each other, may be arrangedobliquely in relation to the direction of travel of the flat-bag carrierwhich then brings the zones of the wide gumming successively to thepoints where the field has its maximum effect and causes dryingstep-by-step.

In the second embodiment, high-frequency electric voltage is preferablyproduced by a magnetron in a waveguide of brass or the like consistingof two parallel ilnes, the lines being divided into an upper and a lowerpair by a slit; the lower pair may be constructed in the form of vacuumpassages. The one end of the waveguide is connected in known manner to awater load, which may contribute several advantages, such as eliminationof reflection of the electric field and absorption of the unused energy.

A conveyor belt, which is perforated, is preferably provided to supportthe closing flaps of the flat bags conveyed along the electrodes orthrough the waveguides for the high-frequency field; suction means forattracting and holding the closing flaps on the conveyor belt are thenprovided below the conveyor belt.

The path of travel of the flat bags to be dried may equally well be inthe form of an are or a curve and the electrodes or waveguides are thenadapted to this shape.

The embodiments of the new method, with the devices appropriate thereto,are illustrated purely diagrammatically in the accompanying drawings. Inthese:

FIGURE 1 is a plan view of an arrangement of rod electrodes andconveying means for the drying of the closing flaps of fiat bags with asingle strip of adhesive;

FIGURE 1A shows an arrangement in which a plurality of flat bags, havingrelatively wide gummed portions, are disposed on a conveyor belt abovewhich there is mounted a pair of longitudinally extending electrodesinclined at a small angle to the direction of travel of the belt so thatall portions of the gummed areas are exposed to an electric field whilethe flaps are subjected to a suction action;

FIGURE 2 is a vertical section through the arrangement taken along theline IIII of FIGURE 1;

FIGURE 3 is a vertical section through the arrangement taken along theline III-III of FIGURE 2, with the vacuum passage omitted;

FIGURE 4 is a plan view of an arrangement of waveguides and conveyormeans for the drying of self-adhesive fiat bags with two strips ofadhesive;

FIGURE 5 is a vertical section through the arrangement shown in FIGURE4, taken along the line V-V of the latter, and

FIGURE 6 is a vertical section through the arrangement shown in FIGURE5, taken along the line VI-VI of the latter.

According to FIGURES l to 3, the two rod-shaped electrodes 1 and 2 aremounted at a distance of a few millimeters above a conveyor belt 3 whichruns over rollers 4, rotating in the direction of the arrows shown inFIGURE 2, at the conveying speed of the machine. Each of the twoelectrodes 1 and 2 comprises a holder 5 and 6, which are secured bybolts or screws 7 to links 8 and 9 respectively. The links 8 and 9 areeach connected by screws 10 to one of the output terminals 11 and 12 ofan electric field high-frequency generator designated by 13. The spacingof the eelctrodes 1 and 2 apart from each other and from the conveyorbelt 3 can be adjusted as desired as a result of the slots in the pars5, 6, 8 and 9, the spacing of the electrodes being preferably adjustedto a desired fraction of the wave length of the electric field.

The conveyor belt 3 is perforated, as shown at 14 in FIG. 1, theseperforations extending throughout the length of the belt. Below theupper run of the conveyor belt 3 there is a vacuum chamber 15 which isprovided with a certain reduced pressure by means of connections througha line 15a with an exhauster, not shown. The closing flaps of theflat-bags 16 are sucked tightly against the surface of the conveyor beltby the action of the vacuum chamber, with the fresh gumming 17 exposed.

The flat-bags 16, the large horizontally extending portions of which areheld by a carrier or conveyor means, shown schematically in FIG. 2, anddesignated 3a therein, included in the flat-bag machine, after havingtheir closing flaps gummed by conventional means (not shown), pass withtheir freely projecting closing flaps over the conveyor belt 3. Theseclosing flaps are moved by the conveyors under the two electrodes 1 and2 through the electric field created between the latter. As a result,the paper and gumming become heated and the gumming dries. If desired,the carrier or conveyor means 3a may be upper and lower conveyor beltshaving their bag conveying runs pressed against each other and theinterposed bags being advanced.

If the conveying speed of the parts to be dried is only slow, while thelength of the adhesive application across the conveying direction isgreat, as in the case of overlapped gummed envelope blanks having gummedsurfaces extending lengthwise across the conveyor belt 3, with orwithout the second conveyor belt mentioned, for example, then theelectrodes 1 and 2, although parallel with one another, are preferablyarranged obliquely in relation to the conveying direction, over thegummed areas, so that the drying begins at one side and is car- :riedover to the other side as the blanks are advanced. This is illustratedschematically in FIG. 1A in which the electrodes 1a and 2a are disposedobliquely to the direction of travel of belt 31) which is perforated andsubjected to the vacuum action in the manner shown in FIG. 2. In thisuse of the invention the belt 3!) may serve to support and conveyrelatively wide gummed areas of the flat-bags 16a while the main bodyportions of the fiatbags are conveyed on an extension of conveyor meansincluded in the flat-bag machine, such as that indicated at 3a in FIG.1.

In FIGURES 4 to 6, 21 is a waveguide of brass or the like.High-frequency electric voltage is supplied to it, at the end designatedby M, for example by a magne tron. The end designated by W is connectedto a waterload having advantages of the character previously stated.This arrangement is known per se. In its major dimension, the waveguideis in the form of two parallel lines 22, 23. It is divided by a slit 24for the passage of the closing flaps to be dried, between an upper part22, 23 and a lower part 22', 23'. The two parallel lines are connectedto one another by bends 25, 25.

A conveyor belt 27 with perforations 28, which passes around two rollers26 rotating in the direction of the arrows, is arranged to have itsupper run pass through the slit 24 and serves to support the endportions of flatbags 30 with self-adhesive gumming 31 (only mentioned byway of example). The main body portions of the fiatbag 30 may besuitably supported and conveyed by carrier or conveyor means similar tothat designated 3a in FIG. 2. The lower part 22 23' of the waveguide isconnected in a suitable way with suction means to provide a vacuum forholding down the closing flaps on the conveyor belt 27. Internal wallsdesignated 22a and 23a are provided vertically in the region indicatedin FIG. 4 for enabling suction to be created within the parts 22' and 23of the waveguide. Suction for this purpose is created by a connection22'b extending from part 22 of the waveguide to a suitable vacuumproducing source.

If the waveguides 21 to 23 receives high-frequency electric oscillationsfrom the magnetron, an electric field prevails in its interior.Electrical energy is converted directly into heat in the paper or thegumming of the flatbags which are moved longitudinally through theportion of the waveguide that is divided by the slit 24, and so thegumming is dried.

Both the examples of the method described can be used for the drying ofdextrin, latex and other known adhesives. The conveyor belt 3 or 27 andthe vacuum passage 15 must consist of a material which does notconcentrate the electrical energy in itself in a high-frequency electricfield and convert it into heat, for example fiuorocarbon resins, such aspolytetrafiuoroethylene with or without propylene groups, availableunder the trade mark Teflon.

The invention is not restricted to the examples of embodimentsillustrated. The path of travel of the fiatbags to be dried may, forexample, be circular if the flat-bags with exposed closing flaps areheld on the circumference of a drum by means of a belt. This arrangementhas the advantage that the closing flaps are stiffened as a result ofthe curvature so that the conveyor belt 3 or 27 can be omitted.Furtheremore, more than two electrodes 1 and 2 may be used or, whendrying in the interior of a waveguide, this waveguide may be arranged inonly one line or in more than two parallel lines.

Other modifications or embodiments of the constructions disclosed may bemade within the scope of the appended claims.

What is claimed is:

1. A method of drying moist gum on the closure flaps of fiat-bags,envelopes or the like during their passage through a machine for makingthe same, comprising advancing the gummed flaps along a path adjacent toat least two spaced, electrodes which extend substantially in theconveying direction and between which there is produced a high-frequencyelectric field, and applying suction to the gummed flaps to maintainthem in fiat condition against a surface on which they are beingadvanced along said path.

2. A method according to claim 1 in which the electrodes are rod-shapedand the electric field is directed substantially parallel to the surfaceof the sheet material.

3. A method according to claim 1 wherein the gummed flaps are advancedthrough a slit formed in a waveguide to provide portions arranged aboveand below the path of travel of the gummed flaps, and substantiallyparallel with the longitudinal direction of the active portion of thewaveguide, thereby serving to direct a high-frequency electric fieldperpendicular to the surface of the gummed flaps.

4. An apparatus for drying moist gum on the closure flaps of flat-bags,envelopes or the like which comprises: means for conveying the gummedflaps along a predetermined path, rod-shaped electrodes mounted at ashort distance from and substantially parallel with the path of travelof the gummed flaps, a high-frequency generator connected with saidelectrodes adapted to create a highfrequency electric field between theelectrodes which is directed substantially parallel with the surface andtransversely to the direction of travel of the gummed flaps, carriermeans for the main body of the flat-bags, which is movable at theconveying speed of said conveying means for supporting the gummed flaps,and suction means cooperating lwith said conveying means to hold thegummed parts smoothly thereon.

'5. An apparatus according to claim 4 in which said conveying meanscomprises a perforated conveyor belt.

6. An apparatus according to claim 4 in which the conveying means andthe suction means are formed of materials which are not affected 'by theelectric field.

'7. An apparatus according to claim 4 characterized in that the rodelectrodes are parallel with one another and are arranged obliquely inrelation to the direction of travel of the flat-bags so that successiveportions of wide gummed areas come successively to the region in whichthe field has the strongest action.

8. An apparatus for drying moist gum on the closure flaps of flat-bagswhich comprises: means for conveying successive fiat-bags having saidclosure flaps with moist gum thereon along a predetermined path, awaveguide which is fed with high-frequency electromagnetic energymounted parallel with the path of travel of the flat-bags, saidwaveguide being provided with an elongated slit, said means forconveying the flat-bags being arranged to carry their gummed flapsthrough said slit and along the region in Which the high-frequencyelectric field is established in the interior of the waveguide anddirected substantially across the entire width of the gummed flaps asthe latter pass along said slit in the waveguide, and means for creatingsuction in the part of said waveguide below said slit to retain thegummed flaps against the conveying means.

' in that one end of the waveguide is connected to a water load.

11. An apparatus according to claim 8 in which said conveying meanscomprises two separate carriers which are movable at the same conveyingspeed, one of said carriers supporting the gummed parts thereof, andsaid suction means cooperating with said one of the carriers to hold thegummed parts flat on the latter.

12. An apparatus according to claim 11 in which said one of the carrierscomprises a perforated conveyor belt.

13. An apparatus according to claim 11 wherein said one of the carriersand the suction means are formed of materials which are not heated bythe electric field.

14. An apparatus according to claim 11 characterized in that said one ofthe carriers is arranged to pass through the slit in the waveguide whichis divided by this slit into an upper portion and a lower portion andthe lower portion of the waveguide being connected with the means forcreating suction.

References Cited by the Examiner UNITED STATES PATENTS 2,212,522 8/1940Hart et a1. 341 X 3,082,710 3/1963 Holland 12910.81 X 3,197,601 7/1965Wayne et al. ll910.6l X

FREDERICK L. MATTESON, JR., Primary Examiner. JOHN J. CAMBY, Examiner.

1. A METHOD OF DRYING MOIST GUN ON THE CLOSURE FLAPS OF FLAT-BAGS,ENVELOPES OR THE LIKE DURING THEIR PASSAGE THROUGH A MACHINE FOR MAKINGTHE SAME, COMPRISING ADVANCING THE GUMMED FLAPS ALONG A PATH ADJACENT TOAT LEAST TWO SPACED, ELECTRODES WHICH EXTEND SUBSTANTIALLY IN THECONVEYING DIRECTION AND BETWEEN WHICH THERE IS PRODUCED A HIGH-FREQUENCYELECTRIC FIELD, AND APPLYING SUCTION TO THE GUMMED FLAPS TO MAINTAINTHEM IN FLAT CONDITION AGAINST A SURFACE ON WHICH THEY ARE BEINGADVANCED ALONG SAID PATH.